A POROUS MEDIA MODEL FOR SPRINKLER WETTING

摘要

A one-dimensional porous media model has been developed to investigate water based firesuppression. The model is for heat and mass transfer in porous materials subjected to external watersprays and radiant heating. In the model, heat transfer inside the material occurs by conduction,convection, and phase change. Mass transfer occurs by gas phase diffusion and convection in the liquidand gas phases. Convective mass fluxes are driven by pressure gradients according to Darcy’s law.Boundary conditions that are appropriate for a range of cases are presented. The model was used, alongwith experiments, to investigate two scenarios relevant to water based suppression: spray wetting andradiant heating. Ceramic fiberboard samples were used as a test material. For the wetting tests, the modelis shown to be able to reasonably predict the rate of water absorption into the samples. Radiant heatingtests were conducted in the cone calorimeter with pre-wetted samples. For the heating tests, the model isshown to reasonably predict the drying behavior that would directly precede an ignition event.